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HET3 > 303I: Final Drive Fundamentals & Service > Flashcards

303I: Final Drive Fundamentals & Service Flashcards

1
Q

Identify two functions of a final drive system.

A
  • Torque multiplication - Reduction configuration
  • Absorb shock loads imposed on the powertrain due to operation in harsh off-road environments. Abuse

303I Pg. 2

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2
Q

Planetary final drive systems can be identified as ______ mounted or _______ mounted.

A

Inboard & Outboard

303I

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3
Q

Explain what is meant by the term outboard mounted, when describing planetary final drive systems.

A

The location of the planetary final drive system.
An outboard mounted planetary final drive is positioned at the wheel or sprocket as opposed to being mounted to each side of the bevel gear case.

303I Pg. 3

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4
Q

List one disadvantage of an inboard mounted final drive.

A

Size of the output shaft must increase substantially to manage the increased output torque of the final drive.

303I Pg. 6

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5
Q

The final drive housings on many motor graders act very similar to which component of an on-highway truck?

A

Walking beam

303I Pg. 8

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6
Q

On wheeled equipment, the most common gearing configuration used in single planetary final drives is a:

A

First speed reduction

303I Pg. 11

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7
Q

Chain drives are typically simpler in design and more cost effective to produce and operate than comparable gear boxes. (T/F)

A

True

303I Pg. 13

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8
Q

The inverter phase module on an AC drive system converts ______ to ______ for the traction motors when in propel mode.

A

DC to AC for the traction motors in propel mode

303I Pg. 22

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9
Q

The choppers in an AC drive system control the amount of current flow through the:

A

Resistive grids during dynamic braking

303I Pg. 22

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10
Q

A low DC bus voltage must be verified prior to working in which areas of an AC drive system?

A

All areas which are exposed to high voltage

303I Pg. 27

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11
Q

What are the two layers of gloves that must be worn when working on high voltage drive systems?

A

Rubber inner and leather outer gloves
Rated for a minimum 5000 volts

303I Pg. 29

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12
Q

What is the minimum safe working distance for a technician wearing full PPE when testing an AC drive system for high voltage?

A

30 cm / 12” from any conductive component until the voltage is confirmed to be less than 50 Volts DC

303I Pg. 29

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13
Q

Tracked equipment may be equipped with the following 4 types of final drive systems:

A
  • Spur gear single reduction
  • Spur gear double reduction
  • Planetary gear single reduction
  • Planetary gear double reduction

303I Pg. 30

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14
Q

When a planetary final drive is used on a tracked machine, the last gear reduction is between the drive sprocket and the track chain. (T/F)

A

False

303I

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15
Q

How are final drive components typically lubricated?

A
  • Splash lubrication

Filtering By:
- No filtering (maybe a magnetic drain plug to catch metallic particles)
- Remote filter cart used during scheduled maintenance
- Onboard pressure lubrication & filter system

303I Pg. 38

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16
Q

AC drive systems usually have higher _______ then DC systems.

A

Efficiency

303I Pg. 16

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17
Q

Why do AC drive systems use solid-state inverters without any moving parts?

A

Solid state inverters are faster and more responsive

303I Pg. 16

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18
Q

Are AC drive machines generally more or less fuel efficient than mechanical drive machines?

A

More efficient

303I Pg. 17

19
Q

What are some advantages of AC drive over mechanical drive?

A
  • Long component lifespans
  • Relatively maintenance free
  • The ability to run the diesel engine at a constant speed
  • No gear shift shock increases overall drivetrain life
  • Engine and generator are often exchanged as a unit which limits downtime
  • Great retarding abilities, saving mechanical brakes
  • Less oil consumption over their lifespan due to the lack of the transmission torque converter and differential oils

303I Pg. 17

20
Q

The brushless generator is an electro mechanical device that converts _____ energy from the diesel engine into _______ energy

A

Mechanical to electrical

21
Q

What are the five functions of the main control group?

A

1) Converts three phase AC from the generator into DC bus voltage through rectifier assemblies.
2) Converts DC bus voltage to three phase AC for the wheel traction motors through phase modules.
3) Protects the phase modules and the dynamic retarding inverter by using capacitors to filter and store DC bus voltage as well as absorb any transient DC voltage spikes.
4) Controls the amount of DC bus voltage flowing to the dynamic retarding grids by operating the high-voltage contactors and the retarder chopper
5) Regulates the speed of three phase AC retarding grid blower motor by controlling the operation of the dynamic retarding inverter

303I Pg. 19

22
Q

During propel mode, how do the inverters and AC drives control system control the speed and torque of the traction motors?

A

By using a PWM signal to convert DC bus voltage into variable three phase AC for the wheel traction motors.

303I Pg. 20

23
Q

Which configuration of planetary final drive allows for smaller power train components upstream? (Inboard or Outboard)

A

Outboard

303I Pg. 4

24
Q

An advantage of the outboard planetary final drive is ease of maintenance and servicing. (T/F)

A

True.

25
Q

How do you calculate the overall ratio of a planetary gear set when there is more than one stage group?

A

Multiply the two gear ratios together

303I Pg. 37

26
Q

What weight of excavator would use a double reduction reverse planetary final drive?

A

Common up to 20,000 KG (44,000 pounds)

303I Pg. 37

27
Q

What weight of excavator would typically use a triple reduction reverse final drive?

A

Above 20,000 KG (44,000 pounds)

303I Pg. 37

28
Q

Final drive lubricants can be specially formulated to: (4)

A
  • Withstand high operating temperature
  • Flow well at low ambient temperature
  • Provide extreme pressure protection for gear teeth
  • Provide the frictional characteristics required for wet brake and clutch systems

303I Pg. 38

29
Q

Many finals are not vented to atmosphere. Why?

A

Due to their rotational operation.

This lack of venting often causes pressurization. Exercise caution when removing the check/fill plug.

303I Pg. 41

30
Q

Why would a manufacture recommend to drain final drive oil while it is still hot?

A

To ensure oil will drain quickly and completely, and carry suspended contaminants with it.

303I Pg. 41

31
Q

Why is the chain drive preferable in a grader or skid steer application

A
  • Walking beam system provides suspension
  • Ground clearance
  • Chain drive absorb the shock loads as tires travel over obstructions

303I Pg. 9

32
Q

Why are smaller outboard planetary final drives used on smaller articulated trucks ?

A

They allow for smaller components, reducing weight and allow for higher speeds

303I Pg. 11

33
Q

On an outboard mounted planetary drive with a removable centre cover, why might you want access to the sun gear?

A
  • To service
  • To remove in order to tow the vehicle

303I Pg. 3

34
Q

For a planetary gear set to operate as a deep reduction, what components would be the drive, driven, and held members?

A

Sun Gear - Drive
Planet Carrier - Driven
Internal Gear - Held

303I Pg. 11

35
Q

What is the path of power in a double reduction planetary final drive?

A

First Stage:
- Axle shaft
- Sun Gear
- Planet Carrier

Second Stage:
- Sun Gear
- Planet Carrier - Output and bolted to wheel assembly

303I Pg. 12

36
Q

In AC drive equipment, what is an advantage of rectifying the generator’s AC output at the control cabinet?

A

Rectifying it at the control cabinet instead of in the generator housing allows for better cooling.

303I Pg. 18

37
Q

In AC drive equipment that operates on three phase power, how many rectifying diodes would be used?

A

Six. Two for each phase.

303I Pg. 18

38
Q

What DC bus voltage can be reached in an AC drive unit?

A

Over 2000 VDC

303I Pg. 19

39
Q

During dynamic braking in an AC drive unit, the drive motors are driven in an ______ configuration through the trucks final drives.

A

Overdrive

303I Pg. 22

40
Q

PWM is a ratio of:

A

On time to total time

41
Q

On AC Driven equipment, what test could be done to test the engine and generator?

A

Self-load test - AKA Loadbox

303I Pg. 24

42
Q

In an AC Drive control system, how is the DC buss voltage discharged during a normal shutdown?

A

By briefly firing the braking choppers

303I Pg. 25

43
Q

What is a disadvantage of spur gear final drives?

A

Produce high radial loads at the gears
Require strong bearings

303I Pg. 33

HET3 (34 decks)

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